PUBLIC HEALTH ASSESSMENT
BANGOR NAVAL SUBMARINE BASE
AND
BANGOR ORDNANCE DISPOSAL (USNAVY)
SILVERDALE, KITSAP COUNTY, WASHINGTON
PATHWAY ANALYSIS/PUBLIC HEALTH IMPLICATIONS
The following section discusses the various contaminants of concern, how people might come into contact with these contaminants and the potential health effects that may result. In order for an exposure to these contaminants to occur, all the elements of an exposure pathway must be in place. Exposure pathways are divided into completed and potential and can be current, past or future. A completed exposure pathway consists of five elements: source, environmental media/transport, point of exposure, route of exposure and receptor population. A potential exposure pathway exists when some but not all of these five elements are present and the potential exists that the missing elements have been present (past), are present (current) or will be present (future). The completed and potential exposure pathways for Bangor are given in Tables 2 and 3 below. Each pathway is then discussed in terms of the contaminants of concern and the potential health hazard posed.
Chart 1. Pathways Analysis Diagram
Evaluating Non-cancer Risk
In order to evaluate the potential for non-cancer adverse health effects that may result from exposure to contaminated media (i.e., air, water, soil, and sediment), a dose is estimated for each contaminant of concern. These doses are calculated for situations (scenarios) in which nearby residents or on-base workers might come into contact with the contaminated media. The estimated dose for each contaminant under each scenario is then compared to ATSDR's minimal risk level (MRL) or EPA's oral reference dose (RfD). MRLs and RfDs are doses below which non-cancer adverse health effects are not expected to occur (so called "safe" doses). They are derived from toxic effect levels obtained from human population and laboratory animal studies. These toxic effect levels can be either the lowest-observed adverse effect level (LOAEL) or a no-observed adverse effect level (NOAEL). In human or animal studies, the LOAEL is the lowest dose at which an adverse health effect is seen, while the NOAEL is the highest dose that did not result in any adverse health effects.
Due to the uncertainty in these data, the toxic effect level is divided by "safety factors" giving the lower and more protective MRL or RfD. If a dose exceeds the MRL or RfD, this indicates only the potential for adverse health effects. The magnitude of this potential can be inferred from the degree to which this value is exceeded. If the estimated exposure dose is only slightly above the MRL or RfD, then that dose will fall well below the toxic effect level. The higher the estimated dose is above the MRL or RfD, the closer it will be to the toxic effect level.
Evaluating Cancer Risk
Some chemicals have the ability to cause cancer. Cancer risk is estimated by calculating a dose similar to that described above and multiplying it by a cancer potency factor, also known as the cancer slope factor. Some cancer potency factors are derived from human population data. Others are derived from laboratory animal studies involving doses much higher than are encountered in the environment. Use of animal data require extrapolation of the cancer potency obtained from these high dose studies down to real-world exposures. This process involves much uncertainty. Current thinking suggests that a very small dose of a carcinogen will give a very small cancer risk. Cancer risk estimates are, therefore, not yes/no answers but measures of chance (probability). Such measures, however uncertain, are useful in determining the magnitude of a cancer threat since any level of a carcinogenic contaminant carries an associated risk. Some evidence suggests that certain chemicals considered to be carcinogenic must exceed a threshold of tolerance before initiating cancer.
This document describes cancer risk qualitatively using terms like low, very low, slight and no significant increase in cancer risk. Cancer risk estimates are used to help environmental agencies know when to take action to clean up hazardous waste sites or conduct health actions. Cancer risk estimates are theoretical. Actual risk may be as low as zero. These terms can be better understood by considering the population size required for such an estimate to result in a single cancer case. For example, a low increase in cancer risk indicates an estimate in the range of one cancer case per ten thousand persons exposed over a lifetime. A very low estimate might result in one cancer case per several tens of thousands exposed over a lifetime and a slight estimate would require an exposed population of several hundreds of thousands to result in a single case.
ATSDR considers theoretical cancer risk not to be significant when the cancer risk estimate results in less than one cancer per ten thousand exposed over a lifetime. Cancer risk estimates less than one cancer per ten thousand are therefore considered to pose no apparent public health hazard. The reader should note that these estimates are for excess cancers that might result in addition to those normally expected in an unexposed population.
Cancer is a common illness and its occurrence in a population increases with age. Depending on the type of cancer, a population with no known environmental exposure could be expected to have a substantial number of cancer cases. There are many different forms of cancer that result from a variety of causes; not all are fatal. Approximately one quarter to one third of people living in the United States will develop cancer at some point in their lives.
Multiple Exposure and Toxicological Mixtures
A person can be exposed by more than one pathway and to more than one chemical. Exposure to multiple pathways occurs if a contaminant is present in more than one medium (i.e., air, soil, surface water, groundwater, and sediment). For example, the dose of a contaminant received from drinking water may be combined with the dose received from contact with that same contaminant in soil.
It is much more difficult, however, to assess exposure to multiple chemicals. In almost every situation of environmental exposure, there are multiple contaminants to consider. The potential exists for these chemicals to interact in the body and increase or decrease the potential for adverse health effects. The vast number of chemicals in the environment make it impossible to measure all of the possible interactions between these chemicals. Individual cancer risk estimates can be added since they are measures of probability. When estimating non-cancer risk, however, similarities must exist between the chemicals if the doses are to be added. Groups of chemicals that have similar toxic effects can be added such as volatile organic compounds (VOCs) which cause liver toxicity. Polycyclic aromatic hydrocarbons (PAHs) are another group of chemicals that can be assessed as one added dose based on similarities in chemical structure and metabolites. Although some chemicals can interact to cause a toxic effect that is greater than the added effect, there is little evidence demonstrating this at concentrations commonly found in the environment.
The following evaluations do not rely solely on whether the estimated dose of a contaminant exceeds its health comparison value (i.e., MRL, RfD, cancer risk levels). Factors such as background exposure, a growing scientific data base and the inherent uncertainty in assessing health risk are considered when formulating conclusions. These evaluations are based on current data and subject to change should more data become available relative to the site and/or the toxic potential of the contaminants.
Table 3. Completed exposure pathways for Naval Submarine Base, Bangor
| # | Area of Exposure | Source | Contaminant | Media | Point of Exposure | Route of Exposure | Exposed Population | Persons Exposed a |
Time |
Health Risk
|
Comments |
|
| Non- cancer |
Cancer | |||||||||||
| 1 | Mountain View Road | OU-8 | VOCs (1,2-DCA) |
Groundwater | Residential wells | Ingestion Dermal Inhalation |
Off-base Residents | 75 | Past | No | Very Low | No current or future pathway exists since Mountain View residents are supplied with Silverdale water. |
|
2 |
Hood Canal/ Cattail Lake |
Sites OU-1,4,6,7 | Ordnance compounds, phthalates | Fish/ Shellfish | Hood Canal, Cattail Lake Beaches | Ingestion | On and Off-base Residents | 500 | Past | No | No | Only trace levels of contaminants found in sediment and shellfish. |
| 500 | Current | No | No | |||||||||
| 500 | Future | No | No | |||||||||
| 3 | On-base Hazardous Waste Sites | All Operable Units | Ordnance compounds | Soil | All sites | Ingestion Dermal Dust Inhalation |
Workers | 1000 | Past | No | Very low | Current exposure has been reduced or eliminated by remedial actions |
Table 4. Potential exposure pathways for Naval Submarine
Base, Bangor
| # | Area of Potential Exposure | Source | Contaminant | Media | Point of Exposure | Route of Exposure | Exposed Population | Time | Comments |
| 1 | On-base Supply Wells | OU-2 and 4 | Ordnance Compounds | Groundwater | Bangor supply wells | Ingestion Dermal |
On-base residents & workers | Future | Wells in sea-level and aquifer unlikely to be impacted. |
| 2 | Vinland Supply Wells | OU-1 | Ordnance Compounds | Groundwater | Vinland public & residential wells | Ingestion Dermal |
Off-base Residents | Future | Groundwater is not moving in the direction of wells. |
| 3 | Olympic View/ Old Bangor Supply Wells |
OU-2 | Ordnance Compounds | Groundwater | Olympic View/Old Bangor public and residential wells | Ingestion Dermal |
Off-base residents | Future | Contamination is still about a mile away from off-base wells. |
B. Completed Exposure Pathways
No apparent public health hazard exists for people in the Mountain View Road area who drank 1,2-dichloroethane (1,2-DCA) contaminated residential well water prior to 1995. Chemicals in groundwater originating from the Public Works area of Bangor have contaminated residential wells in the Mountain View Road area. The primary contaminant of concern in residential wells is 1,2-dichloroethane (1,2-DCA) although benzene has been detected at high levels in off-base monitoring wells. No current exposure exists because the Navy provided hook up to Silverdale public water supply for all residences within the groundwater contamination zone.
One private well (PW-16) may have been contaminated with 1,3-dinitrobenzene (1,3-DNB) as early as 1984. Although subsequent testing did not confirm this detection, exposure to 1,3-DNB was also evaluated for users of this well. Exposure to 1,3-DNB the level initially detected in this well does not pose a health hazard.
Groundwater contamination in the Mountain View Road area was first reported in October 1984 when 19.3 ppb 1,3-dinitrobenzene (1,3-DNB) was detected in residential well PW-16 (Figure 7). No contaminants were found in any of the other 14 residential wells sampled at that time. Subsequent sampling and analysis of off-base and on-base wells over the next year revealed conflicting results. A sample taken from PW-16 in July/August of 1985 showed 13.2 ppb 1,3-DNB according to one lab but no detections were reported by a second lab that analyzed the same sample. A similar discrepancy was reported from samples collected in November 1985.12 Although 1,3-DNB has been found at Site F (OU-2), two rounds of groundwater samples at Site 25 (OU-3) found no 1,3-DNB. Analysis of a sub-surface soil samples from a well boring at Site 25 did detect 1,3-DNB at 51 ppb.7 Site 25 is the location of a former wastewater discharge pond adjacent to the Mountain View Road area.
In May 1986, investigations of a potential gasoline release in the Public Works facility bordering the Mountain View Road area identified a significant amount of groundwater contamination in the area. Based on the amounts of free product detected in groundwater monitoring wells, it was determined that approximately 20,000 gallons of gasoline had been spilled since 1982. A recovery system was installed in August 1986 to recover the gasoline from the groundwater. No residential wells were sampled at this time.4
In February 1994, analysis of a sample taken by the local health department from a new residential well (PW-01) detected volatile organic compounds (VOCs) and the herbicide bromacil. Additional sampling in March 1994 confirmed these detections but no contaminants were found in seven other residential wells. Further investigation of groundwater in the Public Works and Mountain View Road areas detected contaminants in both on and off-base groundwater.4 Maximum levels of contaminants of concern found in off-base monitoring and private wells are given in Appendix C, Tables C1 and C2 (see Figure 7 for well locations). High levels of these contaminants were found in on-base groundwater including 1,2-DCA at a maximum of 1,700 ppb and benzene at a maximum of 9,800 ppb. During these investigations, the base provided bottled water to residents in the Mountain View Road from April 1994 through the end of 1995 when residences were connected to Silverdale public water. In May 1997, a groundwater containment/treatment system became operational joining the existing gasoline recovery system.13
The extent of the off-base 1,2-DCA contaminant plume is illustrated in Figure 8. Contaminants from the gasoline spill follow the same path as the chlorinated solvents. However, it is likely that the chlorinated solvent plume originated earlier since virtually no chlorinated compounds have been found in soil suggesting that enough time has elapsed to allow any surface spills to completely wash through soil into groundwater. Both contaminant plumes are confined within a narrow lateral boundary of the surface aquifer extending southeast from the Public Works area as far as Clear Creek Road. The surface aquifer in this area extends down as far as 250 feet before reaching a confining clay layer. Contaminant depth increases as the plume extends off-base indicating vertical as well as lateral movement from the source.
A quarterly monitoring program of residential wells in the Mountain View Road area has been ongoing since the first quarter of 1995. Although the initial detection of 1,2-DCA came from a residential well that was never in use, later sampling found declining levels of 1,2-DCA in two other residential wells (PW-08 and PW-04). Initial sampling of PW-08 and PW-04 in first quarter 1995 found 1,2-DCA at 4.6 and 0.42 ppb, respectively. These results represent the maximum level of 1,2-DCA found in these or any residential well in the area. Low levels of other VOCs have been intermittently detected in residential wells. Chart 2 below gives the sampling history for residential well PW-08.
Chart 2. 1,2-Dichloroethane Levels in Mountain View Road Residential Well PW-08
1,2-Dichloroethane (1,2-DCA)
The provision of Silverdale public water to residents in the Mountain View Road area has eliminated exposure to groundwater contamination originating in the Public Works area of Bangor. However, residents using wells PW-08 and PW-04 as a drinking water source prior to the provision of alternate water were exposed to 1,2-DCA through ingestion, inhalation and dermal contact.
Non-cancer Effects
Non-cancer
adverse health effects are not expected to result from past exposure
of residents to the maximum level of 1,2-DCA ever found in Mountain View Road
drinking water wells. No current exposure pathway exists since residents
in affected area have been connected to the Silverdale public water supply.
The estimated dose calculated for a resident exposed to the maximum detected
level of 1,2-DCA in drinking water (4.6 ppb in PW-08) is 500-fold below ATSDR's
intermediate minimal risk level (MRL).17
However, residential wells PW-08 and PW-04 have shown declining levels of 1,2-DCA since testing began in April 1994. This trend indicates that levels of 1,2-DCA could have been higher prior to initial testing. It is also important to note that no chronic MRLs or RfDs are available for 1,2-DCA. Chronic MRLs and RfDs are usually lower than intermediate or acute MRLs because they are derived from studies in which the dose was given over a longer periods of time. The toxicity of 1,2-DCA is discussed further in the Toxicological Evaluation section (see page 34).
Cancer Effects
EPA has classified
1,2-DCA as a Group B2 probable human carcinogen based on evidence of blood vessel
tumors that developed in rats given high doses of 1,2-DCA. Although there is
no supporting evidence that 1,2-DCA can cause cancer in humans,a cancer potency
factor was derived by EPA from the animal study mentioned above.18
Using this cancer potency factor (called a slope factor), a very low cancer
risk was estimated for a child growing to adulthood over a 30-year period while
exposed to the maximum detected level of 1,2-DCA. This level which over-estimates
the actual exposures presents no apparent public health hazard.
The source of the 1,2-DCA contamination of private wells in the Mountain View Road area is assumed to be near the highest levels of 1,2-DCA found in groundwater at the Public Works facility. However, no information has been located with which to estimate the quantity or date of any discharge of these types of chemicals. Although levels of 1,2-DCA could have been higher in Mountain View Road residential wells prior to initial testing, there is no current information to predict what those levels might have been.
1,3-Dinitrobenzene
It is possible, but not certain, that residents using private well PW-16 were exposed to 1,3-DNB in drinking water. Although the initial detection of 1,3-DNB in this well was not confirmed, the chemical was detected once more in this same well and in on-base monitoring wells. Available data were insufficient to conclude that these detections were lab errors. Therefore, residents using well PW-16 prior to the provision of alternate water are assumed to have been exposed to 1,3-DNB. This exposure would have been primarily through ingestion but dermal absorption may also have contributed. Inhalation of 1,3-DNB volatilizing from water is not expected to be a significant route of exposure.
Non-cancer Effects
Adverse health effects are not likely to result from past exposure of residents to 1,3-DNB in residential well PW-16. No current exposure pathway exists since residents using PW-16 have been connected to the Silverdale public water supply. The toxicity of 1,3-DNB is discussed further in the Toxicological Evaluation section (see page 36).
Cancer Effects
There is no evidence to suggest that 1,3-DNB is carcinogenic.
No apparent public health hazard exists for residents living in the Mountain View Road area who drank contaminated groundwater that originated at the Bangor Public Works facility (OU-8). Residents have been connected to the Silverdale public water supply since December 1995.
Exposure of residents to 1,3-dinitrobenzene was evaluated based on unconfirmed detections of this ordnance compound in residential well (PW-16). The maximum levels of 1.3-dinitrobenzene detected is not likely to result in adverse health effects.
Mountain View Road residents should not use private drinking water wells for domestic purposes until groundwater contaminant levels have declined below a level of health concern for long term use. These wells are currently being monitored for VOC contamination but should be tested for bromacil prior to resumption of use as a domestic water supply.
No public health hazard exists for base personnel or off-base shellfish harvesters from exposure to contaminants in fish and shellfish taken from Cattail Lake or Hood Canal beaches. Sampling and analysis of sediment, fish and shellfish along Hood Canal and Cattail over the past 10 years has detected very little contamination. Low levels of polycyclic aromatic hydrocarbons (PAHs) were found in sediments along with trace levels of phthalates and ordnance compounds in shellfish from Hood Canal and trout from Cattail Lake. The beaches below the former landfill at Floral Point (Site B) are currently not open to shell fishing. Although sediment and shellfish sampling indicate that the landfill is not a contaminant source, further sampling of shellfish should be conducted prior to reopening of this beach.
Analysis of fish and shellfish samples taken along Hood Canal and Cattail Lake from October 1988 through October 1998 have shown minimal contamination. Contaminants of concern given in Appendix C, Table C3, were selected based on detection for organics and exceedance of background levels for inorganics. Sediment sampling along Hood Canal has consistently shown only sparse and low level contamination.
Sampling of shellfish and sediment along Hood Canal and Cattail Lake dates back to1988 when samples were gathered in support of the RI/FS for Site A (OU-1). Further sampling of Hood Canal sediment and shellfish was conducted in 1991 and 1992 as part of the RI/FS for Site 26 (OU-7).11 Samples were collected from seven areas along Hood Canal from Floral Point south to Carlson Spit (Figure 9). The ROD for OU-7 signed in April 1996 determined that four of these areas (Floral Point, Marginal Wharf, K/B Dock and Service Pier) warranted further sampling. Two more rounds of sediment and shellfish samples were taken from these areas in September/October 1996 and September/October 1998. Shellfish sampling during these last two rounds was limited to the Floral Point area. In 1997, a 12 inch vegetative soil cover was installed over the former landfill in areas of chemical contamination.19
Polycyclic aromatic hydrocarbons (PAHs) were the primary contaminants found in Hood Canal sediments during RI/FS sampling. The most recent sampling of sediment in 1998 showed decreasing concentrations of PAHs at Marginal Wharf, K/B Dock and Service Pier. Sampling of Floral Point sediment and shellfish in 1996 and 1998 was based primarily on the potential for metals to move from the former landfill via groundwater to beach sediments. Maximum concentrations of mercury (3.1 ppm) and lead (629 ppm) had been previously detected in subsurface soil samples taken at the landfill as part of the RI/FS. Also of concern were elevated levels of PCBs (maximum of 6.4 ppm) and pesticides also found in landfill soils at this time. Therefore, analysis of clam tissue from Floral Point during these later sampling rounds included metals, pesticides and PCBs.
An evaluation of Hood Canal sediments released by DOH in July 1997 concluded that Floral Point was the only beach threatened from upland sources of contamination. Although sediment data was deemed inadequate at Floral Point, it was recommended that this beach remain closed to shellfish harvesting based on the proximity of the former landfill.20 It is important to note that this evaluation was based on comparisons with Washington State Sediment Management Standards (SMS). The SMS standards adopted by Ecology use ecological endpoints (i.e., benthic organisms). While these standards may also be protective of human health, the following assessment used tissue data to estimate exposure via ingestion of shellfish.
Very little contamination is evident in sediment and fish/shellfish in any area of Hood Canal or Cattail Lake. Previous assessments have shown decreasing levels of PAHs in sediments and only trace contaminants in shellfish. A dose was estimated for anglers and shellfish harvesters exposed to the maximum levels of contaminants of concern from ingestion of fish from Cattail Lake and shellfish from Hood Canal. None of the estimated doses exceeded respective RfDs or MRLs. The potential for exposure to multiple contaminants was estimated by assuming a "worst-case" scenario of a fish eater exposed to the maximum levels of each contaminant found in fish or shellfish regardless of source. A combined dose was calculated and determined to be below a level of concern when compared with a "combined" reference dose or hazard index.
No adverse health effects are expected to result from ingestion of shellfish from Hood Canal. Past soil sampling indicates that the former Floral Point landfill is a potential source of contaminants metals, PCBs and pesticides in beach sediment and shellfish. The lack of significant contamination on the beach could be explained by the low mobility of PCBs and pesticides in groundwater and the infrequent detection of mercury (2 of 32 samples) and lead (5 of 30 samples) in subsurface soil. It is useful to note that groundwater samples taken near the landfill did not show particularly high levels of these soil contaminants.
No adverse health effects are expected to result from ingestion of fish from Cattail Lake. The amount of 1,2,3-trinitrobenzene (9 ppb) detected in one of two composite samples of cutthroat trout taken from Cattail Lake October 1988 is below a level of health concern. No other contaminants were found in either of these samples. However, these two samples represent the only fish analyzed from Cattail Lake. Site A continues to represent a potential source of contaminants for Cattail Lake via discharge of groundwater containing RDX. Although RDX, as well as most other ordnance compounds, is not expected to bioaccumulate in fish to any great extent, this potential has not been well studied.
No apparent public health hazard exists from ingestion of fish from Cattail Lake or shellfish from Hood Canal. Analysis of fish, shellfish and sediment samples indicate very little contamination.
Shellfish sampling near Floral Point on Hood Canal has been limited to littleneck clams. If the beach below the former landfill is to be reopened for shellfish harvesting, other species that might be available for harvest should be analyzed for metals, pesticides, PCBs and PAHs. These data should be gathered and evaluated by DOH prior to reopening of the beach for shell fishing. More shellfish sampling is scheduled for the Floral point area as part of the Record of Decision.
No apparent public health hazard exists for workers who may have been exposed to contaminants in on-base surface soil prior to remedial activities. Sites-A (OU-1) and Site D (OU-6) posed the greatest chance for exposure of workers to soil contaminants at levels of health concern. Past exposure of workers to ordnance compounds in surface soil during demolition and burning of ordnance is estimated to have resulted in only a low risk for cancer. No current health hazard exists, however, as soil remediation in areas of concern is either ongoing or complete.
Contamination of soil, sediment and surface water has been identified at several sites throughout Bangor. Maximum levels of contaminants of concern detected in surface soil for all operable units is given in Appendix C, Table C4. Extensive sampling of surface water and sediment in Hood Canal, Cattail Lake and Vinland Creek found only trace levels of contamination in these media. This pathway analysis, therefore, considers only exposure to soil. Ingestion of fish from Cattail Lake or shellfish from Hood Canal is evaluated in Pathway 2.
In the past, base personnel may have been exposed to contaminants in soil through accidental ingestion, skin contact and inhalation of dust. Current exposure is assumed to be negligible based on the ongoing or completed remediation at all sites. The primary areas of surface soil contamination include Site A and Site D where the highest levels of ordnance compounds were found. Site F (OU-2) lagoon soils contained high levels of ordnance compounds but were only available for contact by workers during transfer to Site A for disposal. Operable Unit -3 contained the highest levels of arsenic and antimony both of which are listed as contaminants of concern.
The health assessment for workers exposed to contaminants in on-base surface soil focused on Sites A and D as these were the most contaminated sites. It was assumed that a worker could have been exposed to the upper-bound, average concentration for each contaminant of concern found in surface soil at Sites A and D. A maximum value was used for 2,6-DNT as no upper-bound average was available.
Non-cancer Effects
No current public health hazard exists for workers exposed to soil at any hazardous waste sites on base. A low risk for non-cancer adverse health effects exists for past exposure of workers over long periods of time to soil at Sites A and D.
The maximum level or upper confidence limit (95 UCL) of each contaminant of concern found in on-base surface soil was used to estimate a dose for a worker exposed for 250 days/year over a 25 year period. This exposure duration represents the entire length of demilitarization activities at Sites A and D. These doses were then compared with their respective oral reference dose (RfD). The estimated dose for TNT was about 4-fold higher than its respective RfD. No other estimated doses for contaminants of concern in surface soil exceeded their RfDs.
The RfD for TNT is based on liver toxicity seen in rats
given high doses of TNT in a capsule over a 25 week
period. The lowest-observable adverse effect level
(LOAEL) noted in this study is approximately 270 times
higher than the estimated dose calculated for past
exposure of a worker to TNT in soil. Since this estimated
dose exceeds the RfD, but is well below the LOAEL,
adverse health effects are not likely. The RfD for TNT
was set 1000 times lower than this LOAEL in order to
provide added safety for the protection of public health.18
The toxicity of TNT and other ordnance compounds is
discussed further in the Toxicological Evaluation section
(see page 35).
The estimated doses for each contaminant of concern were added to provide an overall estimate of non-cancer health risk. This combined exposure did not result in a significant increase in health risk. It is important to note that some chemicals can cause more than an additive effect when combined, in which case this assessment will underestimate the potential for adverse health effects. There is little evidence, however, of such synergistic effects between chemicals at levels commonly found in the environment.
The non-cancer risk calculated for TNT applies to exposures of intermediate as wells as long-term duration (i.e., several weeks or longer). This risk is primarily due to high levels of TNT in surface soil at Sites A and D. It is important to note that this risk is based on a "worst-case" scenario and is highly dependant upon duration of exposure and work practices. Those workers using personal protective equipment or who were not frequently involved in demilitarization activities at Sites A and D would have had significantly less exposure.
Cancer Effects
A low cancer risk was estimated for workers exposed under the same scenario used above and does not pose a public health hazard. Several ordnance compounds including RDX, TNT, 2,4 and 2,6-DNT and arsenic contributed to this risk estimate. Each of these chemicals have been classified by EPA as known, probable or possible human carcinogens (see Appendix C for class descriptions and Table C1 for specific classifications).18 The majority of this risk is attributable to the ordnance compounds with a small percentage coming from arsenic. Also, included in this estimate was di(2-ethylhexyl) phthalate (DEHP) which, along with other similar chemicals called phthalates, are common environmental and laboratory contaminants due to their presence in plastics. The contribution of DEHP to the overall cancer risk is negligible.
Cancer risk estimates made in this health assessment utilized a cancer potency factor (CPF) derived by EPA from animal data. The relevance of cancer caused in laboratory animals at high doses for humans exposed to much lower levels found in the environment is questionable. Such animal data is considered to be much stronger when supported by evidence of cancer in humans. There is little evidence, however, to show that any of these ordnance compounds can cause cancer in humans. In order to relate these high dose animal exposures to lower environmental exposures, estimates are made using mathematical equations. These mathematical equations are used to derive a CPF that can be used to estimate risk. A discussion of cancer risk estimation is given in the introduction of the Pathways Analysis section (see page 12). The toxicity of ordnance compounds is discussed further in the Toxicological Evaluation section of this document (see pages 35 and 36).
No current public health hazard exists for workers or other base personnel exposed to surface soil at hazardous waste sites located on-base. Remedial activity is either ongoing or completed at each operable unit and has effectively reduced or eliminated exposure to below a level of health concern.
No apparent public health hazard existed for past exposure of workers to contaminants in on-base surface soil primarily at Sites A and D. Exposures of several weeks or more to ordnance compounds in soil during burning and demolition at these sites represents a low increase in risk for cancer . The magnitude of this risk would have been significantly reduced by protective clothing and other gear.
No recommendations are necessary to reduce exposure to soil contaminants as remedial measures have already been taken.
C. Potential Exposure Pathways
Groundwater contaminants at Site A (OU-1) are not expected to impact off-site drinking water wells in the nearby community of Vinland located on the norther border of the base. Ordnance compounds detected in the shallow aquifer are expected to move primarily towards Cattail Lake. No contaminants have been found in the deeper sea-level aquifer. Continued monitoring of MW-28 will ensure detection of any groundwater contaminants moving towards drinking water wells in Vinland.
Site A was used to burn and explode ordnance between 1962 and 1986 resulting in contamination of soil, surface water and groundwater (Figure 10). Groundwater contamination at Site A has been found in both the perched and shallow aquifers.1 The perched aquifer is subject to large seasonal variation since its sole recharge source is rain infiltration. Groundwater moves north from this aquifer and surfaces during the wet months in a marsh prior to discharge into Vinalnd Creek Water in the perched zone can also move vertically into the shallow aquifer. Groundwater in the shallow aquifer around Site A moves west/northwest discharging to Cattail Lake and Hood Canal. The deeper, sea level aquifer is a major regional water bearing unit that extends across the Kitsap Peninsula and discharges to both Hood Canal and Liberty Bay. It is separated from the shallow aquifer in the area of Site A by 140 to160 feet of dense, low permeability silt.1
RDX and TNT are the primary contaminants in the perched aquifers while lower levels of other ordnance compounds have also been detected. RDX is the primary contaminant in the shallow aquifer although trace levels of TNT have also been found. No ordnance compounds have been detected in the sea-level aquifer. The maximum level of RDX ever detected in monitoring wells at Site A is 1,000 ppb found in MW-48. The most recent sampling of Site A monitoring and extraction wells in the Spring of 1999 found RDX at a maximum of 500 ppb in extraction well EW-7 (Figure 11).21
The community of Vinland is located on the northern border of the base within 1500 feet of Site A. There are currently two municipal supply wells serving approximately 2,400 Vinland residents with an additional five wells available for emergency supply. A well survey conducted during the RI/FS process located private and public supply wells in Vinland area in both the shallow and sea level aquifers (Figure 12). Two municipal wells were located by this survey directly north of Site A in the sea level aquifer. One of these wells (PUD-1) is located on the border of the base while the other (PUD-2) is located 1500 feet to the north. These two municipal supply wells along with some private residential wells were sampled in August 1989. A slight detection of TNT was recorded for PUD-2 (0.01 ppb) along with 0.02 ppb RDX in residential well 5L1. Both of these reported values, however, were below their respective sample detection limits. These wells were apparently sampled again in October 1989 but the results of this sampling were not located.1 It is not clear whether PUD-1 and PUD-2 are still in service as part of the Vinland public water supply. No ordnance compounds were found in any other off-site wells.
Remedial efforts have been ongoing at Site A since December 1994. A leach basin was constructed in which burn area soils were placed. Leachate collected from rain infiltration is routed to a activated carbon filtration system where ordnance is removed from the leachate before discharge into the leach basin. Leachate will be directly discharge to this area once cleanup requirement are met. In addition to soil cleanup, a groundwater extraction system is removing contaminated groundwater that is also routed to the filtration system for ordnance removal before discharge to a drainage area east of Cattail Lake.22
The most recent sampling of monitoring wells in the burn area shows that RDX in the shallow aquifer remains high with a maximum of 200 ppb. However, sampling of shallow monitoring wells MW-28 and MW-30 located on the north border of the base near Vinalnd have consistently detected no contaminants or only trace levels of RDX and TNT. The trace detections in 1989 of TNT in PUD-2 and RDX in private well 5L-1 are not consistent with the expected movement of groundwater or the lack of significant detections in MW-28 and MW-30. Since the detections in 5L-1 and PUD-2 were below the method detection limit, verification would have been necessary to confirm these results. Although these wells were apparently sampled again one week later, the data were not located. It is possible that the detections in PUD-1 and 5L1 were the result of field contamination or lab error.
It is unlikely that the small amount of TNT in the shallow aquifer at Site A could reach PUD-2 which is located in the sea-level aquifer about 1,500 feet northeast of the base boundary. It is also not clear whether this well is still in service. Private well 5L-1 is located at a depth of 70 feet in the shallow aquifer and is approximately 500 feet downgradient from MW-28 which is screened at about 80 feet. Regular sampling of MW-28 since 1991 has failed to detected any ordnance compounds. However, detection limits in MW-28 sample analyses have risen from 0.02 ppb in 1991 to 1.5 ppb during the most recent sampling in February 1999.
Ongoing remediation along with the lack of any off-base groundwater contamination indicates little chance for future exposure of Vinland residents to contaminants in drinking water originating from Site A. Shallow groundwater at Site A moves primarily to the west in the direction of Cattail Lake. The lack of any recent detections of TNT or RDX in monitoring wells MW-28 and MW-30 indicates that drinking water wells in the Vinland area are not threatened by Site A contaminants.
Contaminants in groundwater at Site A do not appear to be moving in the direction of Vinland and are not likely to be a threat to drinking water wells along this border of the base.
Annual sampling of MW-28 as part of the ongoing remediation at Site A should ensure that any contaminants moving in groundwater towards Vinland will be detected. Detection limits for samples analyzed from MW-28 should not exceed the current level of 1.5 ppb.
Site F (OU-2) is the location of a former unlined wastewater lagoon that received effluent from demilitarization activities from 1960 through 1970. These activities resulted in contamination of the shallow aquifer with ordnance compounds including RDX, TNT, 2,4-DNT and 2,6-DNT. No contaminants have been found in the deeper sea-level aquifer. Remedial efforts have been ongoing at Site-F since December 1994. The current containment and monitoring system in place at Site-F will either prevent or detect further movement of contaminants, specifically RDX, in the shallow aquifer. Since off-base wells are still about one mile from the leading edge of the RDX plume, current monitoring will provide ample warning should the plume move beyond the containment system. The inactive base supply well SO6 should be sampled to ensure that ordnance compounds have not reached the sea-level aquifer.
Site F is the location of a former unlined wastewater lagoon that received effluent from demilitarization activities from 1960 through 1970 (Figure 13). Effluent discharged to the lagoon consisted primarily TNT, RDX, 2,4-DNT and 2,6-DNT and was commonly known as "pink water." The lagoon was excavated to an average depth of about five feet in the till overlying the shallow aquifer and had an overflow channel that ran south to an undetermined area. Contaminants in lagoon wastewater have penetrated into the surface aquifer below but have not been detected in the deeper sea-level aquifer. This sea-level aquifer is protected by a thick (80-100 foot) layer of dense, low permeability silt located beneath the shallow aquifer that retards the downward movement of contaminants. Groundwater in the shallow aquifer flows northwest at a rate of 200 feet per year and discharges via seeps to an unnamed creek that runs through the town of Old Bangor. Downward movement of groundwater through the aquitard separating the shallow and sea-level aquifers is estimated at one foot per year. The sea level aquifer is a major regional water bearing unit that extends across the Kitsap Peninsula and discharges to both Hood Canal and Liberty Bay.2
The primary ordnance compounds detected in the shallow aquifer include RDX, TNT, 2,4-DNT and 2,6-DNT. Groundwater sampling during the RI/FS between September 1990 and April 1992 detected RDX, TNT and total DNT in the shallow aquifer at maximums of 7,120, 8,900 and 540 ppb, respectively. The most recent sampling of monitoring wells at Site F in January 1999 detected an overall maximum level of RDX at 1,300 ppb in MW-39, TNT at 5,800 ppb in MW-31 and total DNT at 358 ppb in MW-31.22
Remedial efforts have been ongoing at Site F since December 1994. Soil from the lagoon area was excavated, composted and returned prior to the installation of an infiltration barrier. A pump-and-treat groundwater remediation system was put in place to both contain and remove contaminants from the plume.
Groundwater monitoring and remediation of the shallow aquifer is ongoing at Site-F. Although high levels of RDX, TNT and DNTs are still present near the former lagoon, only RDX has traveled significantly beyond this source area. RDX has never been detected in MW-65. MW-65 is the furthest monitoring well from the source (approximately 4,200 feet northwest) and has been sampled since May 1998 (Figure 14). However, MW-63, approximately 3,000 feet from the source, contained 120 ppb RDX during the most recent sampling in January 1999. MW-64, located between these two wells and about 3,500 feet from the source, showed 2.5 ppb RDX in the January 1999 sampling and represents the outer edge of the RDX contaminant plume.23 MW-64 is estimated to be 5,400 feet away from the northwest border of the base where the residential communities of Olympic View and Old Bangor are located.
Although there has never been any contamination detected in the sea-level aquifer, no sampling data after 1992 was located for wells in this aquifer. As shown in Figure 14, base supply well SO6 is located about 1,500 feet northwest of MW-64 in the sea-level aquifer at a depth of 330 feet. This well has not been used as a drinking water supply since 1990 when sampling detected trace levels of VOCs.23 Off-base private and municipal supply wells are located in the communities of Old Bangor and Olympic View in both the shallow and sea-level aquifers downgradient from Site F. The contaminant plume is currently about one mile from these wells.
The groundwater containment system appears to be keeping the RDX plume from moving beyond the reintroduction wells as evidenced by the low RDX results in MW-64 and the consistent lack of RDX in MW-65 since September 1997. Regular sampling of monitoring wells located at the leading edge of the RDX plume should ensure that any advancement of the plume in the shallow aquifer will be detected. These monitoring wells lie between the plume and the reintroduction wells that serve to return treated water back into the ground. Since it is essential to keep the leading edge of the plume in front of the reintroduction wells, regular sampling of monitoring wells at the edge of the plume is required to ensure proper operation of the groundwater containment system. Recent recommended changes to the Compliance Performance Monitoring Plan for Site F include continued sampling of primary wells twice per year and secondary monitoring wells once every two years.24
The current containment and monitoring system in place at Site F will either prevent or detect further movement of contaminants, specifically RDX, in the shallow aquifer. Since off-base wells are still about one mile from the leading edge of the RDX plume, current monitoring will provide ample warning should the plume move beyond the containment system.
Although the sea-level aquifer is protected by an aquitard, there has been no sampling of this aquifer near Site F since 1992. The presence of inactive supply well SO6 provides a means to sample the sea-level aquifer at the leading edge of the plume.
Monitoring wells at the edge of the Site F contaminant plume should continue to be sampled for ordnance compounds on a regular basis to ensure that the plume does not reach beyond the containment system and threaten shallow wells in the Old Bangor and Olympic View communities.
Bangor supply well SO6 is currently not in use. If this well is ever re-activated for use as a drinking water supply, it should be sampled for ordnance compounds in addition to any other required sampling.
All of the Bangor supply wells are located in the sea-level aquifer which is separated from the shallow aquifer by an aquitard of varying thickness. No groundwater contaminants have been detected in the sea-level aquifer near Site F (OU-6) or Site D (OU-2) which are the only sites proximal and upgradient of active on-base supply wells. A contaminant plume containing ordnance compounds originating from Site F does exist in the shallow aquifer. The currently inactive base supply well, SO6, is approximately 1,500 feet beyond the leading edge of this plume while the active base supply wells are 2 miles away. Periodic sampling of SO6 will ensure that any migration of contaminants from shallow groundwater near Site F into the sea-level aquifer will be detected.
The locations of each Bangor public supply well is shown in Figure 6. Currently, only wells SO1, SO2, SO4 and SO9 are active sources of drinking water for the base. All other sources shown in Figure 6 are either abandoned, inactive or used as supplies for irrigation and/or fire prevention. All of the on-base supply wells are located in the sea-level aquifer which is separated from the shallow aquifer by an aquitard of varying thickness.24 Based on the location of hazardous waste with respect to the active supply wells, only Site D and Site F are in a location that could potentially impact these sources. Both of these sites have contaminant plumes associated with past demilitarization activities.
Each of the active supply wells are required to be sampled regularly for VOCs, metals other contaminants. However, ordnance compounds are not part of this requirement. Low levels of ordnance compounds were detected in the perched aquifer at Site D but no ordnance compounds were found in the shallow aquifer. A significant groundwater contaminant plume containing primarily ordnance compounds does exist in the shallow aquifer at Site F. As discussed previously, RDX is the major contaminant of concern in this plume and has been detected as far as 3,500 feet from the source. The edge of this plume is still approximately two miles from the nearest active on-base supply well (SO1). No contaminants have been detected in the sea-level aquifer near Site F. The shallow and sea-level aquifers are separated by an aquitard that slows downward vertical migration of water and contaminants.
Groundwater contaminants have not been detected in the sea-level aquifer near Site F or Site D which are the only sites proximal and upgradient of active on-base supply wells. The contaminant plume at Site F appears to be restricted to the shallow aquifer but has extended about 3,500 feet beyond its source. An inactive supply well (SO6) is located in the sea-level aquifer about 1,500 feet downgradient of the plume. Discussions with Bangor personnel indicate that VOCs were detected in this well before its use a supply well was discontinued. These detections may have been the result of improper sampling.
SO6 is the most likely base supply well to be impacted if contaminants were to reach the sea-level aquifer. If this well is ever put back into use as a drinking water supply, contaminant testing should be conducted that includes ordnance compounds. In addition, periodic testing of this well would ensure that any ordnance compounds that might reach the sea-level aquifer would be detected well before they reach active, downgradient supply wells.
Contaminants have not been detected in the sea-level aquifer at any sites that could threaten on-base supply wells. Active on-base supply wells are currently protected from ordnance compound in the shallow aquifer near Site F by distance (approximately two miles) and an aquitard that will significantly slow downward migration to the sea-level aquifer. One inactive on-base supply well, SO6, is close to the shallow aquifer plume associated with Site F. Sampling of this well would ensure early detection of an ordnance compounds that move from this plume into the sea-level aquifer.
Bangor supply well SO6 is currently not in use. If this well is ever re-activated for use as a drinking water supply, it should be sampled for ordnance compounds in addition to any other required sampling.
1,2-Dichloroethane (1,2-DCA) is a volatile, organic chemical used as a cleaning solvent. It is mobile in groundwater and will volatilize from water during showering and other domestic uses. Therefore, exposure to 1,2-DCA in drinking water must consider the ingestion, inhalation and dermal routes.
Mountain View Road residents were exposed to 1,2-DCA in drinking water prior to the provision of an alternate water supply. The dose estimated for a child exposed over several years to 1,2-DCA in drinking water at the maximum detected level of 4.6 ppb is more than 500-fold below ATSDR intermediate-MRL.16 This comparison indicates that no acute or intermediate adverse health effects are anticipated at this level of exposure. Although a chronic oral MRL or RfD is not available, the limited chronic exposure animal studies available indicate that LOAELs and NOAELs are well above the estimated intake given for this exposure scenario.
1,2-DCA is classified by EPA as a Group B2 probable human carcinogen based on adequate animal evidence and no human data.18 Rats given high oral doses of 1,2 -DCA showed increases in lung and blood vessel tumors.
2,4,6-Trinitrotoluene, commonly know as TNT, is an explosive chemical widely used in a variety of munitions and other explosive devices. The toxicity of TNT has been observed largely through the study of workers exposed in munitions plants during the First and Second World Wars. Damage to the liver and decreased red blood cell counts (anemia) are the most significant effects of TNT exposure and have been demonstrated in both munitions workers and laboratory animals. The ability of TNT and other organic nitrates to oxidize hemoglobin, decreasing the oxygen transport capability of the blood, supports the association between anemia and TNT exposure. Significant reproductive effects such as decreased testes weight have also been seen in animals at very high doses. This finding is supported by one reproductive study of munitions workers that showed sperm malformations.18,25
It is important to note the difference in exposure of munitions workers and those involved in demilitarization activities at Bangor. The assessment given for on-site workers (see page 24) considers exposure to TNT contaminated soil as opposed to direct exposure of munition workers to pure TNT. This consideration results in a lower dose estimate for Bangor workers. Although the dose calculated for these workers exceeds the RfD, it is well below the actual toxic effect level upon which the RfD is based. This toxic effect level, known as a LOAEL, was the lowest dose that showed toxicity (liver damage) in a study of dogs fed high doses of TNT in their diet. As described in the introduction of the Public Health Implications section, LOAELs are divided by "safety factors" to yield RfDs.
TNT is classified by the EPA as a Group C possible human carcinogen based on sufficient evidence of carcinogenicity in animals and no evidence in humans. Rats given very high doses of TNT in their diet developed bladder cancer. One recent study did show an increased risk for leukemia in a German population that lived near a munitions factory during the Second World War.18,25 However, this study is complicated by a lack of exposure characterization and the likely presence of other chemicals. Cancer risk associated with workers involved in demilitarization activities is discussed in the Public Health Implications section under completed exposure Pathway 3 (see page 24).
2,4 and 2,6-DNT are the primary isomers found in technical grade dinitrotoluene (DNT). Most of the DNT produced is used to manufacture other chemicals. However, it is also used in the manufacture of munitions which explains its presence at Bangor. The toxicity of DNT is has been largely observed from animal studies. DNT has displayed a wide range of toxicity in high dose animal studies that includes effects on the liver, kidneys, blood, immune, nervous, developmental and reproductive systems.26
There is some evidence in humans to support these effects at lower doses. Studies of workers occupational exposed to DNT have reported general central nervous system effects such as dizziness and headaches. One study found an increase in mortality from heart and circulatory disease in workers exposed to DNT. A study of workers employed in a munitions factory during the Second World War noted an increase in cyanosis and anemia although exposure was not quantified and probably involved other chemicals. The ability of DNT and/or its metabolites to form methemoglobin supports the finding of cyanosis and anemia in these workers.26
On-base workers could have been exposed to DNT through direct contact with surface soil during past demilitarization activities. Exposure of workers to the levels of 2,4 and 2,6-DNT found in soil at Bangor is estimated to result in doses much lower than those used in animal studies or predicted for workers employed in manufacturing and munitions plants. In addition, estimated doses are well below the RfDs and MRLs established for these two chemicals.
The EPA has classified the mixture of 2,4 and 2,6-DNT as a Group B2 probable human carcinogen based sufficient data in animals and no evidence in humans. High dose of this mixture caused liver tumors in rats.18 Cancer risk associated with workers involved in demilitarization activities is discussed in the Public Health Implications section under completed exposure Pathway 3 (see page 24).
Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX or Royal Demolition Explosive) is manufactured solely as an explosive compound. There is little evidence of RDX toxicity in humans although adverse effects have been found in laboratory animals. Adverse effects on the nervous system, liver, kidneys and blood have been noted in animals given high doses of RDX. An oral RfD was developed by EPA based on inflamation of the prostate gland seen in rats given high doses of RDX.18,27
On-base workers could have been exposed to RDX through direct contact with surface soil during past demilitarization activities. The dose estimated for a worker exposed to RDX in on-base surface soil is well below this RfD. The EPA has classified RDX as a Group C possible human carcinogen based sufficient data in animals and no evidence in humans. High dose of this mixture caused liver tumors in mice.18 Cancer risk associated with workers involved in demilitarization activities is discussed in the Public Health Implications section under completed exposure Pathway 3 (see page 24).
1,3-Dinitrobenzene (1,3-DNB) is manufactured as both an explosive and a chemical intermediate. The major targets of 1,3-dinitrobenzene toxicity are the blood and male reproductive systems as demonstrated in high dose animal studies. Although no human evidence is available to support these findings, they are consistent with the toxic endpoints observed for TNT and DNT.18,28
EPA has established an RfD for 1,3-DNB based on increased spleen weight in rats given high doses of 1,3-DNB in drinking water.18 A dose estimated for an adult exposed over several years to the maximum detected level of 1,3-DNB is 5-fold higher than this RfD. However, this dose is still 2,000-fold below the actual level that produced the adverse spleen effect. As described in the introduction of the Public Health Implications section, "safety" factors are used to set the RfD well below the actual toxic effect level (i.e., LOAEL). The relative risk of a dose that exceeds the RfD can be judged by how close it is to the actual toxic effect level.
EPA has not classified 1,3-DNB with respect to its carcinogenicity (Group D). No data was located relative to the ability of 1,3-DNB to cause cancer.
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A. Introduction
